In fact, the most cited meta-analysis on whey protein supplementation looked mostly (68%) at studies that included only men.

Hence, the researchers wanted to fill in that knowledge gap by conducting their own meta-analysis and systematic review exploring whey protein supplementation in women.

They looked at randomized, placebo-controlled trials with all healthy women participants, as well as studies with healthy participants of both sexes in which isolated data on just the women participants were available.

Out of 1845 possible whey protein supplementation trials collected through several databases, only 13 studies met these criteria for meta-analysis and review.

“A majority of the research is conducted in male-only populations,” ​lead author Robert Bergia, a graduate research assistant at Purdue, told NutraIngredients-USA.

“A preponderance of evidence supports the beneficial effects of whey protein supplementation on body composition in men; however, there is currently insufficient evidence to make an equivalent claim in women,” ​he argued in the report, published recently​​ in the journal Nutrition Reviews​.

“Addressing this gap in the research and perception were the primary motivators [​of conducting this study].”​

He co-authored the paper with professor of nutrition science Dr. Wayne Campbell, who served on the National Dairy Council’s Whey Protein Advisory Panel, and postdoctoral research associate Joshua Hudson.

Results: Modest increases in lean mass, no change in fat mass​

This contrasted the only other meta-analysis with data on how whey protein supplementation may affect fat mass (most look at changes in lean mass), the researchers reported.

“The present findings in a female-only population are inconsistent with ​[previous] results because there was no detected effect of whey protein supplementation on changes in either fat mass or body mass,” ​they wrote.

No link between ‘bulkiness’ and supplementation​

The researchers also wanted to explore anecdotal data from a consumer survey, which suggests that women believe whey protein supplementation may lead to a bulkier build.

Dairy Management, Inc. and the US Dairy Export Council commissioned the survey conducted by GfK Market Research in 2014. It involved 763 respondents completing a 25-min self-administered survey.

"There is a public perception that whey protein supplementation will lead to bulkiness in women, and these findings show that is not the case,"​ said Dr. Campbell.

Their meta-analysis suggested that "whey protein supplementation favors a modest increase in lean mass of less than 1%, while not influencing fat mass."​

But overall, the women-specific data are in agreement with the majority of meta-analyses of both sexes, such as an increased robustness of whey protein’s effect on lean mass when energy restriction (i.e. eating less calories) was added into an intervention protocol, the researchers added.

They concluded: “Although more research is needed to specifically assess the effects in varying states of energy sufficiency and exercise training, the overall findings support consumption of whey protein in women seeking to modestly improve body composition.”​